Engineers are constantly seeking improved performance and expanded capabilities for fuel systems, while also seeking to reduce risks of structural damage, including cracks, occurring in fatigue sensitive locations of the fuel systems. For example, it has been shown that injection at higher fuel pressures may provide improved performance and efficiency. As a result, fuel system components should be manufactured to withstand these high fuel pressures, especially at locations subject to cyclic stresses, vibrations, and other fatigue causing stresses. For example, the SAC area of the fuel injector, which generally includes the volume underneath the needle check valve seat that opens to the nozzle orifices, may experience extreme fluctuations in pressure and flow forces during and between injection events. In another example, other fuel system components, including high pressure fuel lines, may experience substantial stress due to increased fluid operating pressures, and may also experience other fatigue inducing stresses, such as bending, due to engine vibrations and the like.
It has been shown that a number of surface treatments may improve fatigue life in components where failure may be caused by surface initiated cracks. For example, resistance to crack formation and general material strengthening may be obtained by the application of mechanical shot peening processes, autofrettaging, grinding operations, carburizing heat treatments, ultrasonic impact treatments, and other similar surface treatments. Such treatments, which are applied directly to the fatigue sensitive surface of the component, may effectively increase the fatigue strength of the component, as compared to otherwise untreated components. More recently, as shown in Japanese Patent Publication Number 2006322446, laser shock peening is being used to strengthen a surface of a component to a greater depth than that possible with conventional shot peening. Specifically, the cited reference teaches the use of laser shock peening to increase the strength of a conical seat surface at a branch hole of a fuel system common rail. However, while such strategies for material strengthening are known, many strategies are not available to address fatigue sensitive surfaces, such as those in fuel systems, that, due to size and/or location, may be inaccessible.
The present disclosure is directed to overcoming one or more of the problems set forth above.